The concept of regenerated flow of hydraulic fluid from one end of the hydraulic cylinder back to the other end of the hydraulic cylinder is known. The systems are generally provided to combat excessive movement of the piston in one direction as sometimes occurs under load conditions where gravity is assisting movement. Under such circumstances, the flow requirements may be beyond the capacity of the flow delivery means such as the pump which may result in cavitation or the induction of air somehow into the hydraulic system which will then render the system ineffective.
One system that purports to overcome the above problem is described in U.S. Pat. No. 4,913,616 issued Apr. 3, 1990 to Dunn. The particular system described in this patent relates to a control for bucket movement in an excavator wherein dumping of a loaded bucket requires excessively fast flow to one end of the hydraulic cylinder (one side of the piston) and the control for initiating the dumping action causes restriction of the flow from the other end of the cylinder (other side of the piston) back to the reservoir which results in an increase in the pressure from the other end of the cylinder thereby slowing movement but when the pressure exceeds a preset pressure a check valve is opened to permit flow from the other cylinder end (the out flowing end of the cylinder) to the inflowing end of the cylinder and thereby supplement the flow of fluid into the inflowing end of the cylinder.
The concept of using squash plates or the like to pump hydraulic fluid in one direction or the other direction in a hydraulic circuit is well known.
It has also been suggested with double acting hydraulic systems having fluid chambers with the same effective cross sectional areas so that the amount of fluid entering one of the double acting cylinders is equal to the amount of fluid leaving the other cylinder to use a pump to increase the pressure as required when the fluid is moved from one of the double acting cylinders to the other. During movement of the piston of the double acting system one of the chambers functions as a source and the other as the receiving chamber or vice versa without any imbalance in the system. Such an arrangement is shown in U.S. Pat. No. 4,738,101 issued Apr. 19, 1988 to Kubik.
U.S. Pat. No. 4,359,931 issued Nov. 23, 1982 to Palmershein et al discloses a double acting piston and cylinder wherein flow from the smaller cross sectional area side of a piston (i.e. piston rod side) is directed to the opposite side of the piston when the piston is to be extended.